1. Field of the Invention
The present invention relates to methods for the removal of unwanted human hair and, more particularly, to methods of removing unwanted human hair permanently.
2. Description of the Related Art
There are three cycles in development of the human hair. The first is the resting stage; the second, the growing stage and the third is the shedding stage. In the resting stage, relatively dormant hair cells are present in the epidermis of the skin and are not seen above the skin surface. These hair cells may stay dormant for years. They outnumber the adult or growing hairs by at least 5 to 10 times.
In the growing stage, hair follicles develop downward from the epidermis into the dermal layer. A hair bulb is connected to a small capillary which feeds the hair follicle and its adjacent cellular structures. Research studies have documented that there are many sites in the hair structure which are capable of follicular regeneration. Furthermore, to achieve permanent hair removal, even the sebaceous glands must be destroyed. Therefore, when one simply plucks the hair shaft out, a new hair will grow back in its place.
The currently available hair removal methods include, among others, the traditional electrolysis treatment in which a tiny needle is inserted into the skin down to the hair follicle. Using an electrical direct current, the salt (sodium chloride) ions in the hair follicle are converted into sodium hydroxide which destroys the hair follicle and its adjacent cells. This method is rather painful and carries risks of infection and scarring.
Further, even in the hands of a trained operator, one can never be certain of the accuracy of the placement of the needle tip. This method is very time consuming, requiring about 1 minute to treat each hair. However, when the needle is placed correctly, this method is known to be the most effective one presently available.
The thermolysis method of hair removal is similar to the electrolysis method in that accurate placement of a needle is required for hair destruction. In this case, heat generated in the needle tip causes an inflammatory reaction around the follicle which, in turn, destroys the hair follicle and its adjacent cells.
The thermolysis method is much quicker than the electrolysis method, only requiring 1 to 2 seconds to destroy the hair follicle. It is less effective than electrolysis and requires the accurate placement of a needle.
The blend method is a hybrid of the electrolysis and thermolysis methods. A tiny needle is inserted down to the follicle. Both direct current electrical energy and radio frequency radiant energy are carried down the needle to the site of the follicle. The needle tip conducts a direct current which converts the sodium chloride molecules to sodium hydroxide, as in electrolysis, and the radio frequency components generate heat in the surrounding tissues which causes the inflammatory reaction produced in the thermolysis method. The heat also acts as a catalyst to speed up the destructive process of the alkaline ions. This method is as effective as the electrolysis method and requires 10 to 15 seconds for each hair. However, neither the risks of electrolysis nor thermolysis are reduced.
All of the above described methods work only on hairs in the growing stage and have no effect on hairs in the resting or shedding stages of development.
In the patent to Weissman et al, U.S. Pat. No. 4,388,924, it was proposed that a laser be used to photo-coagulate and therefore devitalize the blood circulation feeding the hair follicles. Where Weissman et al discussed earlier patents that utilized xenon lamps, Weissman et al suggested the use of a laser that could produce a light beam that would penetrate the skin with little or no absorption of energy at the surface, but which would deliver most of the light energy to the hair root.
Weissman et al proposed an argon laser, operating between 480 and 520 nm which would be highly absorbed in the hair root causing coagulation of the blood vessels in the area. However, the method required selective aiming at individual hairs and a complex treatment apparatus was described.
In the patent to Zaias, U.S. Pat. No. 5,059,192, it was suggested that a Q-switched ruby laser, operating at a wavelength of 694 nm, would be absorbed by the melanin concentration at the base of the hair follicle. The absorption of the laser energy by the melanin would cause photothermolysis and melanasomal disruption, including vaporization of the melanin in the follicle.
Other direct effects included vacuolation, edema, gas bubbles and protein denaturation, seriously injuring the follicle and the hair cells in the earlier stages of development. If sufficient energy is delivered by the laser, the hair producing cells are effectively destroyed and there is no regrowth.
An apertured plate was recommended so that different parts of the body could be treated. For example, a 3 mm plate would be used with scalp hairs while openings of from 5 to 8 mm would be used with other body parts. The process could be applied to individual hairs or could treat up to 3 or 4 hairs on the body. The recommended exposure dosages ranged from 0.4 J/cm.sup.2 to 10.0 J/cm.sup.2 with a suggested optimum of 8.0 J/cm.sup.2. Pulses in the range of from 30 to 40 nanoseconds duration were recommended.
More recently, the patent to Tankovich, U.S. Pat. No. 5,425,728, suggested that the photothermolytic effects of the lasers could be enhanced by utilizing contaminants with high absorption of the frequencies employed by the source of radiant energy. The contaminants included carbon in a peach oil which, with massage or ultrasound, could be used to force the carbon into the hair ducts. For this contaminant, a CO.sub.2 laser was recommended, with pulses of widths between 200 and 275 ns at repetition rates of from 8 to 30 Hz applied to a 1 cm.sup.2 spot and delivering from 0.1 Joules to 0.2 Joule per pulse.
An alternative method uses a near infrared laser at about 1,060 nm but with pulses in the range of 25-30 picoseconds. The energy per pulse was from 3-6 mJ and the spot size was from 0.1 to 0.3 cm.sup.2. Another alternative utilized a staining technique and matched the laser to the stain selected. Yet another option was the use of a photosensitizer which made the entire hair shaft susceptible to the applied laser.
These most recent laser methods using red and infrared wavelength are much quicker than the earlier treatments in that the laser can act upon a group of hairs in a fraction of a second. Also, the use of the laser is somewhat less painful and has a much lower risk of infection and scarring than any of the methods mentioned above.
However, all of the laser methods rely on the phenomenon of the laser energy being absorbed by the melanin in the hair follicle, or by a dye or other contaminant, all of which generate heat from the absorbed energy and essentially "burn" the follicle. Where the melanin is the primary target, pulse width is very important because if the pulse width is less than the thermal relaxation time of melanin, the thermal reaction will be confined mainly to the melanin. In such a case, insufficient heat will be generated outside of the melanin to destroy the entire hair follicle, let alone the adjacent apigmented cells.
When the pulse width is greater than the thermal relaxation time of the melanin, the hair follicle is destroyed by the heat. However, some of the surrounding apigmented cells will be injured by the heat released by the absorption of the laser energy by the melanin.
However, as flux or fluence and/or the pulse width of the laser is increased, the risks of scarring, and changes in pigment, and skin texture become proportionally increased. These risks can be reduced slightly but not eliminated by methods such as cooling the hand piece and by the use of topically applied heat sinks such as the gels used with EKG or ultrasound procedures.
To achieve permanent hair removal, it is important to damage or destroy the entire hair follicle, the surrounding apigmented cells, the mid shaft and the sebaceous glands.